Textile process and composition



United States Patent 3,173,751 TEXTILE PROCESS AND COMPOSITION George C. Daul and Thomas F. Brake, both of Mobile, Ala, assignors, by mesne assignments, to Courtaulds, Limited, London, England, a British company No Drawing. Filed Apr. 26, 1961, Ser. No. 105,553 13 Claims. (Cl. 8-116.4)

This invention relates to a method for improving the properties of cellulose, and in particular to a method for cross-linking cellulose by means of formaldehyde, and to composition for eifecting such cross-linking.

For many years it has been known that when cellulose is treated with formaldehyde, various properties, in particular its resistance to swelling by water, are improved. It is considered that such changes occur through cross-linking of the cellulose chains at suitable positions along their length. Although the ability of formaldehyde to cross-link cellulose has been known for perhaps fifty years, no substantial commercial use has been made of this ability, because the processes so far proposed have all had very serious practical drawbacks.

Chiefiy such processes have not succeeded because they have used acid catalysts which are ditficult to control to avoid excessive tendering of the textile material.

In our copending application Serial No. 81,956, filed January 11, 1961, now Patent No. 3,113,826, we have described the cross-linking of cellulose by means of cer tain metallic salts which are Lewis acids in the solid state. In the procedure described in said application cellulosic textile material is impregnated with formaldehyde and with high concentrations of the Lewis acid. It is then dried and cured by heating. The process described in our prior application has the distinct advantage over formaldehyde treatments in permitting relatively large amounts of formaldehyde to be chemically combined with the cellulose without objectionable tendering. However, with the specific Lewis acids enumerated in said prior application it is preferred to carry out the process at a pH of or above. Below pH 5, it is found, there is a tendency toward tendering of the cellulose material.

The present invention is based upon the discovery that zinc iluoborate is a good catalyst for the cellulose-formaldehyde reaction. In particular it has been found that cellulose, especially regenerated cellulose textile material, can be cross-linked with formaldehyde using Zn(BF as a catalyst at pH 5 without extensive damage. This is a valuable property, since the use of a low pH in general permits a shorter curing time or a lower curing temperature to be used. Shorter curing times have obvious economic advantages. Lower curing temperatures make it possible to use conventional steam dryers for curing, thus enabling the process to be practiced with equipment which is readily available in many finishing plants.

The invention thus envisions a process for cross-linking cellulose which comprises reacting cellulose with formaldehyde in the presence of zinc fiuoborate.

The invention can be applied to any form of cellulose, though it is most useful with regenerated cellulose. Normally the process will find its greatest application in the treatment of filamentary material, though other forms, e.g. paper, board or film may also be treated. The filamentary material may be treated in the form of staple fiber, as continuous filament, or in the form of tow, yarn or thread. The process can also be applied to structures containing cellulose fibers. The structures may be woven or knitted textile fabrics, or textile fabrics of other kinds, for example, the so-called non-woven fabrics, or even paper. The fabrics may be of various constructions; thus they may consist wholly of cellulose fibers or in part of these fibers and in part of fibers of other kinds, for

example, cellulose acetate (acetone soluble cellulose acetate or cellulose tri-acetate), or fibers of synthetic linear polymers, for example, of polyamides, such as nylon 6 or nylon 66, or of polyesters, for example polyethylene terephthalate, or of addition polymers derived from acrylonitrile. The cellulose fibers in the fabrics may be staple fibers or continuous filaments. Preferably, when blends are treated, the cellulose fibers comprise at least by weight of the blend.

If desired, the cellulose, prior to treating may have been dyed with any of many common dyes, without adverse efiect.

The formaldehyde used may be added to the treating solution as the normal 37-40% aqueous commercial solution. Other sources, e.g. paraformaldehyde, may, however, be used as desired.

The zinc fluoborate may be added to the treating solution as the anhydrous salt, or as a hydrate. The commercially available solution containing 40% ZH(BF4) 2.6H20 may also be used.

The formaldehyde and the zinc fluorborate are normally applied from aqueous solutions. Other solvents, e.g. methanol or ethanol, may be present without detrimental effect, but the solution should contain at least 10% by weight water. Separate solutions may be used for the formaldehyde and the zinc iluorborate, but no advantage is gained thereby.

The concentration of formaldehyde in the treating solution may vary to a considerable extent, depending on whether natural or regenerated cellulose is treated and on the physical form of the fiber. Moreover, where high crease recovery is required, more bound formaldehyde is required in the final product and a higher concentration of formaldehyde is used when the objective is merely a decrease in water imbibition.

In general, it is found that the amount of zinc fiuoborate deposited on the cellulose is more significant than the concentration of formaldehyde in the solution, provided that enough formaldehyde is present during curing to furnish the quantity of formaldehyde required to be bound to the cellulose for the effect desired. With this in mind, it is found that while solutions containing large concentrations of formaldehyde (say 10 to 20%) and small concentrations of zinc fluoborate (say 0.06 to 0.2% Zn(BF may be used, it is preferable to use smaller amounts of formaldehyde, and relatively large amounts of Zn(BF The use of smaller amounts of formaldehyde is more economical and creates fewer problems in connection with the health and comfort of operators. Moreover, the use of large excesses of formaldehyde increases the tendency toward odor development in the finished product, requiring extensive washing with resultant increased expense.

In general, a recommended overall concentration range for formaldehyde would be between about 0.5 and about 6%, and for Zn(BF between about 0.3% and about 3.5%.

As noted above one of the advantages of the present invention is that low pH can be used, and preferably the pH of the solution is therefore below about 5, usually between about 1 and about 5, preferably between about 3 and about 5. Above about pH 5, zinc fiuoborate hydrolyses to form a precipitate even at low concentrations.

The temperature of the treating solution is not especially critical; Room temperature is satisfactory, though lower temperatures may be used to prevent loss of formaldehyde. Normally, temperatures of 15 C. to C. are used.

The treating solution may contain various textile auxiliaries such as softening agents, lubricants, water repel- :9 a lants and the like. In general, these materials function in the normal way, i.e. as they would were no formaldehyde present.

The treating solution (or solutions) is applied to the If desired, it may then be subjected to any of a number of conventional after treatments. For example, cellulose fabrics, following treatment by the present process can be mercerized, or sanforized, or both. It is an important cellulose in such a way that after impregnation and dryadvantage of the invention that it permits normaltextile ing the material contains at least 0.2 g. zinc fluoborate, trade regenerated cellulose fabrics to be mercerized or Zn(BF per 100 g. of cellulose and preferably between sanforized.

about 0.35 and about 4.5 g. per 100 g. of cellulose. Suf- As noted above, the product obtained from the present ficient formaldehyde is picked up so that, bearing in mind process contains between about 0.25% and about 2.5% losses during drying and curing, between about 0.25 and 10 formaldehyde chemically bound directly to the cellulose about 2.5% by weight is chemically bound directly to the (based on air dry unimpregnated material), as determined cellulose. Formaldehyde is said to be chemically bound by the amount of formaldehyde liberated by complete if it is not removed by securing in water for one hour hydrolysis of the cellulose with 12 N H 80 at the boil. It may be determined by measuring the When the initial material treated in accordance with quantity of formaldehyde released upon complete hydrol- 15 the invention is regenerated cellulose, the characteristics ysis of the treated cellulose with 12 N H 80 of the product are quite different from those of the start- As indicated previously, the amount of bound forming material. Thus, although normal regenerated cellualdehyde will vary with the effect desired. When fiber lose swells so rapidly in caustic soda that mercerization of is treated as such to reduce water imbibition, 0.25 to say regenerated cellulose fabric is not practical, the product 1.25% by weight bound formaldehyde will be sutncient. of the present invention has a greatly lowered swellability To give crease recovery and dimensional stability to in caustic soda and can be mercerized without difiiculty. textiles 0.5% to 2.5% bound formaldehyde is required. Again, regenerated cellulose will dissolve in cupram- Normally, for reasons of economy, the weight ratio of monium hydroxide, while the products of the present zinc fluoborate to formaldehyde deposited on the fiber invention will not. Further, while the water imbibition of will be at least 1:20 and preferably between about 1:19 conventional textile grade viscose staple fiber is about and about 5: 1. Larger amounts of formaldehyde may be 100115%, the water imbibition of the present products used, but as explained above this is not desirable. can be reduced to around -40%.

The actual manipulative steps by which the treating When cellulose fabrics are treated in accordance with soltuion is applied will Vary with the physical form of the invention, their dry crease recovery is greatly imthe cellulosic material. In the case of staple fiber, a mat 30 proved, and is usually increased by at least 50 (W-l-F). or blanket of the material is normally sprayed with the In some cases it may be increased by as much as 150 solution followed by a squeezing to remove excess. A (W+F). Moreover, permanent dimensional stability is continuous filament may be passed through a path or imparted, even after scouring at acid pH. Since no wound on a roller over which the reagent is sprayed. A chlorine retentive groups are introduced into the cellulose, tow may be laid down in a plaited pattern and sprayed; the resistance of fabric treated in accordance with the inor passed continuously through a bath. Woven and knitvention to damage by chlorine bleaches is high. ted fabrics may be padded using techniques well known The invention will be further described with reference to the art. to the following specific examples which are given for In all of these cases, the treatment "is preferably carpurpose of illustration only and are not to be taken as ried out so that after removal of excess liquor by squeez- 40 in any way limiting the invention beyond the scope of the ing or other means, between say 130% and say 50% of appended claims. liquor (based on the weight of bone dry unimpregnated material) remains on the material. EXAMPLE 1 Following impregnation, the material is dried at say 30110 C. for whatever time is required to reduce the Flfieen gram Samples of r- 11/2 X %6 Vlscose moisture content to say 5% or less by Weight of the bone Y fiber Soaked for 5 31111111165 9 of aqueous dry material and then cured by heating to temperatures Solution having 3 P of f contalnlng 03% 9" from about 110 0. to about 180 c. for periods which aldehyde (from 37% commercial fqrmaldelgyde solutwn) may range from say 30 minutes to a few (say about 5 and from 03% 39% y Welght) Z1110 filloborate Seconds hexahydrate. The samples were centrifuged to about The temperature and time for curing must be carefully 13 0% P P 0f 1iqllid y Weight of bone Sf 6611111086, selected having in mind the pH at which the treatment m at alld Cured at for 6 minutes 111 a has been conducted. Thus where a low pH is used, curing Dletefi y may be conducted under mild conditions within the range The l' f Samples Were rinsed free of catalyst, dfled Set f th i h a rather hi h temperature d a very h t and conditioned. Dry and wet tenaclty determinations time or with a low temperature and a longer time. were made. Part of each Sample Was scoured 9 9 Obviously, the drying and curing Steps may be hour in water at 95-l00 C. and tested for water lmbibibined in Single treatment, if i y t1on value using the procedure described in the Journal of Following the curing stage, the cellulose may be washed, the Society of Dyers and Colourists, October 1948, P if desired, with NH urea or other formaldehyde ac- 3 1. ceptor to remove unbound formaldehyde and curing agent. Results are shown in Table A below.

Table A HOHO Applied, ZIl(BF4)2.6HzO G. Zn(BF4)z, Dry Dry Wet Ten, Water Percent Applied, Percent 100 g. cell. Denier Ten., Elong., g./d. Imbiblg./d. Percent t1on,

Percent None (Control) 1. 50 2. 40 22. 5 1.45 98 a 0. 3 0. 27 1. 54 2. 35 14. 5 1. 49 62 0. 6 0. 54 1. 46 2.43 12.8 1. 5s 48 1.2 1.08 1. 48 2.20 9.2 1.56 41 1.8 1.62 1. 52 1. 7.0 1. 32 37 2.4 2.16 1.50 1. 94 6.5 1. 40 36 3.0 2.70 1.60 2.06 7.3 1. 49 39 3,173,751 6 EXAMPLE 2 minutes and in the cure zone 7 minutes. The fiber product had a water imbibition value of 50%, a dry tenacity of A blallkfit of freshly spuil-Ilevef-drled "156086 TaYOII 2.3 g./d., and a wet tenacity of 1.6 g./d. A control (textile grade) still inthe gel state after spinning and havsample h d a ate imbibition of 100%, a dry tenacity mg a gel-state water imbibition value of 140% was pref 2,5 jd, d a wet tena ity of 1.3 g./d.

squeezed between pressure rolls to a liquid retention of Afte scouring in water at 100 C. for 1 hour, the water about 100% on the weight of cellulose. imbibition value was 48%, and the bound formaldehyde The squeezed blanket was then passed under a spray gonfent was of an aqueous solution containing 1.5% by weight of formaldehyde, 1% by weight of zinc fluoborate hexahyl0 EXAMPLE 3 drate (from a commercial solution) and 0.4% of Samples of a rayon challis were soaked for five minutes a polyglycol stearate finishing agent. The solution had in baths containing varying amounts of formaldehyde and a pH of 3.5. zince fluoborate at pH 3.5, padded to 100% pickup, The impregnation was carried out in two stages with a framed, dried for 10 minutes at C. and cured for five pressurized intermediate squeeze and afinal heavy squeeze minutes at 150 C. or for 3 minutes at 160 C. After (60 lb./linear inch) to a final liquid retention of about curing the samples were washed to remove excess salts,

% on the we1ght of cellulose. pressed dry, analysed and tested.

The treating bath was re-crrculated and replemshed by Results are listed 1n Table B below.

Table B Percent Percent Dry Wet Elm. Tear 2 R-Strip Ten. Bath Make-Up Cure Conditions G. Z11(BF )z, Bound Secured SEA 1 ORA 1 100 g. 001 ECHO W.I. W+F W+F Dry Wet Dry Wet 3.0% HCHO, 1.0% 211031 0). 1. 0 0. 30 54. 7 201 183 1. 0 1. 4 41. 1 13. 4 3.0% ECHO, 2.0% Znt'BFnL 2.0 0. s0 44. 0 214 197 1.2 1. 3 20. 0 15. 7 3.0% H0110, 3.0% Zn(BF4)z 3.0 1.15 42. 4 226 209 0. 9 1. 0 23. 7 13.1 4.5% H0110, 1.0% ZnGZFQg- 1. 0 1. 0 44. 2 207 203 2. 4 2.1 31. 4 19. 1 4.5% HOHO, 2 0% Zn(BF4)z 2. 0 1.1 39. 3 223 210 1. 9 2. 3 24. 0 24. 5 4.5% HCHO, 3 0% 21103332. 3. 0 1. 7 34. 7 241 239 1. 7 2.1 20. 5 14.0 3.0% HCHO. 1.0% zntBFnz 1. 0 0. 37 5s. 0 203 177 2. 4 1. s 23.1 15. 7 3.0% 1101-10, 2.0% 211031702. 2. 0 0. 97 41. 3 222 212 1. 5 1. 3 21. 0 13. 5 3.0% HCHO, 3.0% 21103302 3. 0 1. 03 40. 7 217 207 1. 0 1. 2 1s. 3 9. 8 4.5% HCHO, 1.0% Zn (Bran. 1.0 0. 93 44. 7 200 214 2.1 2. 0 23.1 13.5 4.5% HCHO, 2.0% Zn(BFi)2. 2. 0 1. 3 40. 7 229 225 1. 7 2. 0 17. 0 10.3 4.5 0 ECHO, 3.0% Zn(BF.1): 100 0., 3 min 3.0 1. 9 39.5 240 230 1. 0 2.1 23.3 13.9 Control Fabrin 35 170 160 1. s 1. 2 32. 2 15. 0

1 CRA (W+F)=Monsanto Crease Recovery Angle (Warp and Filling); See 1955 Technical Manual, AATCC, p. 157.

2 Elm. Tear=Ele1nendorf Tear Strength; Testing procedure described in ASTM Standards on Textile Materials D1424; p. 607-611.

R-Strlp Ten.=Ravel Strip Tensile Strength; Testing procedure described 111 ASTM Standards on Textile Materials, October 1959, Tests for woven fabrics, D 39, p. 4.

metering in a concentrated mixture of zinc fiuoborate and EXAMPLE 4 formaldehyde in the correct proportions. Similarly, con- Th procedure f E l 3 was t d at H 5 R centrated finishing agent was added to the bath at a rate suits are shown in Table C.

Table C Percent Percent Dry Wet Elm. Tear R-Strip Ten. Bath Make-Up Cure Conditions G. ZI1(BF;):, Bound Scoured (IRA ORA 100 g. cell. HCHO W.I. W+F W+F Dry Wet Dry Wet 3.0% HCHO, 1.0% 21103111). 150 0., 5 min 1. 0 0. 35 03. 7 195 174 1. 9 1. 6 35. 6 13. 5 3.0% HCHO, 2 0% Zn(BF4)1 150 0.. 5 min 2. 0 0. 09 51 203 186 1. 5 1. 4 29. 7 17.9 3.0% HCHO, 3.0% Zn(BF4)7 150 0., 5 min 3. 0 0. 92 44.9 213 193 1. 3 1. 3 24. 4 14. 5 4.5% E0110. 1.0% 7.11031. L- 150 0., 5 111111.- 1. 0 0.12 '70v 0 201 172 2. 2 1. 5 34.1 17.5 4.5% HCHO, 2.0% Z11(BF4)1 150 0., 5 min 2. 0 1.0 44.7 210 203 1.4 1. 3 29. 4 18.4 4.5% HCHO, 3.0% Zn(BF4)4 150 0.. 5 min. 3.0 1.3 40.0 220 214 1.1 1.2 23.2 15. 0 3.0% ECHO, 1.0% Zn(BF1)1 100 0., 3 min 1. 0 0. 21 69. 5 100 159 2. 2 1. 0 35. 0 19. 2 3.0% ECHO, 2.0% 27110313)! 0., 3 min. 2. 0 0. 02 56. 7 215 187 1. 5 1. 4 29. 9 17.9 3.0% HCHO, 3.0% Z11(BF4)2 100 0 .3 111111.- 3. 0 0. 36 45.3 227 197 1. 2 1. 2 24. s 13. 0 4.5% HOHO, 1.0% znosrng 100 0 ,3 mm 1. 0 0. 25 01. 2 203 17s 1. 3 1. 5 30. 7 15. 3 4.5% HOHO, 2.0% Zn (B3414 16 0.. 3 min 2. 0 1. 1 41.3 230 227 1.1 1. 2 22. 5 12. 2 4.5% ECHO, 3.0% 211031 1): 100 0., 3 min 3.0 1. 0 35.1 243 21s 1. 2 1. 3 20.1 14. 7 Control Fabric 35 170 160 1. 8 1. 2 32. 2 15. 6

suilicient to maintain the correct concentration in the bath.

The treated, squeezed fiber blanket was opened, laid 60 EXAMPLE 5 down as a bed on a conveyor, passed through a drier at The procedure of Examples 3 and 4 wa repeated at H 3 temperature of 105 C. then through a cure zone at a 3.0, with curing at C. for 5 minutes. Results are temperature of C. Dwell time in the drier was 20 shown in Table D.

Table D HCHO, Bath G. ZI1(BF4)z, Bound W.I., Dry ORA Wet CRA Grab percent ZI1(BF4):, 100 g. cell. HCHO, percent W+F W+F Tensile,

percent percent lbs.

The control (untreated fabric) and a Crab tensile of about 48 lbs.

EXAMPLE 6 Three samples of the same rayon challis used in Examples 3-5 were treated in a bath containing 4.5% HCI-IO and 2.0% Zn(BF at pH 2.5. After padding to 100% pickup they were framed to dimension, dried at 80% C. and cured for five minutes at 130 C., 140 C. and 150 C. respectively. After washing and drying they were analysed It is thus obvious that with Zn(BF curing can be carried out efiiciently at relatively low temperatures.

We claim:

1. A method for cross-linking cellulose which comprises reacting cellulose with formaldehyde in the presence of zinc fluoborate.

' 2. A method for cross-linking cellulose which comprises impregnating cellulose with zinc fiuoborate and with formaldehyde in the presence of water and curing the impregnated cellulose.

3. A method for cross-linking regenerated cellulose filamentary material which comprises impregnating said material with formaldehyde and with an aqueous solution of zinc fluoborate and curing the impregnated material.

4. A method for cross-linking regenerated cellulose filamentary material which comprises impregnating said material with formaldehyde and with zinc fluoborate in the presence of water at a pH not greater than about 5, and curing the impregnated material.

5. A method for cross-linking regenerated cellulose filamentary material which comprises impregnating said material, in the presence of water with formaldehyde and with at least about 0.2 g. per 100 g. of cellulose of zinc fluoborate, and curing the impregnated material.

7 6. The method claimed in claim wherein the material is impregnated at a pH between about .2 and about 5.

7. A method for crcssdinking regenerated cellulose filamentary material which comprises impregnating said material with an aqueous solution containing formaldehyde and between about 0.3 and about 3.5% by Weight zinc fluoborate and drying and curing the impregnated material.

8. A method for cross-linking regenerated cellulose filamentary material which comprises impregnating said material with an aqueous solution containing between about 0.5 and about 6% formaldehyde, between about 0.3% and about 3.5% zinc fluoborate and having a pH between "about 2 and about Sand drying and curing the impregnated material.

'9. The method claimed in claim 8 and comprising curing the impregnated material by heating it at between about C. and about C.

10. An aqueous solution for use in cross-linking cellulose comprising formaldehyde and Zinc fluoborate.

11. An aqueous solution for use in cross-linking cellulose comprising formaldehyde and at least about 0.3% zinc fluoborate.

12. An aqueous solution for use in cross-linking cellulose comprising between about 0.5% and about 6% formaldehyde, between about 0.3% and about 3.5% zinc fiuoborate, and having a pH not greater than about 5.

13. The solution claimed in claim 12 wherein the pH is between about 2 and about 5.

References Cited in the file of this patent UNITED STATES PATENTS 2,311,080 Pinkney Feb. 16, 1943 2,436,076 Pfeifer Feb. 17, 1948 2,826,514 Schroeder Mar. 11, 1958 3,046,079 Reeves, et a1. July 24, 1962 FOREIGN PATENTS 721,380 Great Britain Ian. 5, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 5, 173, 751 March 16, 1965 George C. Daul et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below. 7

Column 1, vline 12, for "composition" read compositions line 47 for "pHS" read pH below 5 column 2, line 22, for "fluorborate" read fluoborate line 56, for "used when" read used than when column 3, line 53, for "path" read bath columns 5 and 6, Table B, last column, under "Wet", line 1 thereof, for "18.4" read 18.7 same column and table, line 2 thereof, for "15 7" read 15 .4 same column and table, line 4 thereof, for "19.L'- read 19.7 column 7, line 1, for "and a Crab" read had a Grab column 8, lines 47 and 48,

strike out "Guthrie: Textile Research Journal, vol. 33, pp.995 958, 1963 Signed and sealed this 14th day of September 1965,

(SEAL) Attest:

ERNEST W, SWIDER EDWARD J, BRENNER Attesting Officer Commissioner of Patents 

1. A METHOD FOR CROSS-LINKING CELLULOSE WHICH COMPRISES REACTING CELLULOSE WITH FORMALDEHYDE IN THE PRESENCE OF ZINC FLUOBORATE. 